Know the Science: How Medications and Supplements Can Interact
Drugs With a Narrow Therapeutic Range
Having the right amount of certain drugs in your body is crucial. If the amount of the drug is even a little too low or too high, it can cause big problems.
Drugs like these are said to have a “narrow therapeutic range” or “narrow therapeutic index.”
Interactions are of special concern for drugs with a narrow therapeutic range.
|Examples of Drugs With a Narrow Therapeutic Range|
|Carbamazepine (used to prevent seizures)|
|Cyclosporine (used to prevent organ transplant rejection)|
|Digoxin (used to treat heart problems)|
|Levothyroxine (used to treat thyroid problems)|
|Phenytoin (used to prevent seizures)|
|Warfarin (an anticoagulant—also called a blood thinner)|
If you’re taking a dietary supplement, and your health care provider prescribes a drug with a narrow therapeutic range, what should you do?
Tell your health care provider that you’re taking the supplement and ask the provider what you should do.